Modern vehicles are much more complex than vehicles produced as recently as twenty years ago. One of the most complicated aspects of modern vehicles includes electrical power management amongst systems and communications between systems. In fact, communication between and amongst a vehicle's various systems and subsystems is often implemented using high speed serial bus communication techniques. One such popular serial bus protocol implemented on many vehicle systems is known as the CAN (Controller Area Network) protocol. The CAN protocol is a multi-master protocol for efficiently communicating serial data between a vehicle's systems and subsystems. Other vehicle bus communication protocols are also known such as LIN, MOST, and FLEXRAY. The complexity of vehicle electrical control systems has been exacerbated in recent times by the proliferation of hybrid vehicles. Hybrid vehicles depend upon the combination of both a fossil fuel powered engine and an electric motor to generate a vehicle's propulsion forces.
The efficiency gains promised by hybrid vehicles may in part be attained by the proper monitor and control of the electrical power consumed or generated by one or more vehicle subsystems. It may also be desirable to assign priorities to the various subsystems so that when power demanded by a hybrid vehicle's systems exceeds the vehicle's power generation capability, the highest priority systems can be kept in service while the electrical load imposed by the lower priority systems can be lightened or eliminated.